CBCT在食管癌调强放疗中的摆位误差分析

目的探讨食管癌调强放射治疗（intensitymodulatedradiationtherapy，IMRT）在摆位中行锥形束断层扫描（conebeamcomputedtomography，CBCT）的重要性。方法应用瓦里安Trilogy加速器对15例食管癌患者进行调强放射治疗。每位患者前5次治疗前均行1次CBCT扫描及后续疗程中每周做1次CBCT扫描，然后与计划CT图像配准得到等中心三个方向的位移误差。结果①15例患者共获取140幅图像。三个方向的位移误差分别为垂直方向（1．330±0．307）mm、头脚方向（2．670±0．739）mm、左右方向（1．730±0．434）mm。②患者纠正后垂直方向、头脚方向、左右方向摆位误差均低于纠正前，差异有统计学意义（P〈0．05）。患者治疗后垂直方向、头脚方向、左右方向摆位误差与纠正后比较，差异均无统计学意义（P〉0．05）。结论食管癌调强放疗中行CBCT扫描具有重要作用。食管癌调强放射治疗中，重复摆位存在一定误差，只有分析误差产生原因，采取有效措施减少误差，才能使靶区及周围正常组织器官的剂量分布更准确，为临床放疗提供质量保证。

Error analysis of intensity modulated radiation therapy in esophageal can- cer by CBCT

Objective To investigate the importance of CBCT scan in setup of IMRT for esophageal cancer. Methods Fifteen patients with esophageal cancer were enrolled into the study of IMRT with Varian Trilogy linear accelerator who were scanned by cone beam CT before the first radiotherapy and afterward once a week. The acquired images of CBCT were co-registered with planning CT and displacement errors of three directions were obtained. Results （1）A total of 140 images were received in 15 patients. The displacement errors in three directions were vertical direction （1.330±0.307） mm, head-foot direction （2.670±0.739） mm, left-right direction（1.730±0.434） mm. （2）The displacement errors of vertical direction, head-foot direction and left-right direction after the correction were all lower than those before the correction, the differences were statistically significant （P〈0.05）. The displacement errors of vertical direction, head-foot direction and left-right direction after the treatment compared with those after the correction, the difference was not statistically signifieant（P〉0.05）. Conclusion CBCT scan plays an important role in IMRT for esophageal cancer and the re-setup errors always occur in radiotherapy of esophageal cancer, only analyzing the causes of errors and taking effective measures to reduce errors can make the does distribution of target and normal tissues around the organs more accurate and provide quality assurance for clinical radiotherapy.